Chrome Extension - Use javascript to run periodically, and log data permanently

Question

Currently, I have a script that when the image in the top right tray is clicked(only for one specific allowed website), it scans the pages HTML then outputs some value. This

Answer 1

Chrome limits the frequency of repeating alarms to at most once per minute. If that is OK, here is how to do it:

See here on how to setup an event page.

In the background.js you would do something like this:

// event: called when extension is installed or updated or Chrome is updated
function onInstalled() {
    // CREATE ALARMS HERE
    ...
}

// event: called when Chrome first starts
function onStartup() {
    // CREATE ALARMS HERE
    ...
}

// event: alarm raised
function onAlarm(alarm) {
    switch (alarm.name) {
        case 'updatePhotos':
            // get the latest for the live photo streams
            photoSources.processDaily();
            break;
        ...
        default:
            break;
    }
}

// listen for extension install or update
chrome.runtime.onInstalled.addListener(onInstalled);

// listen for Chrome starting
chrome.runtime.onStartup.addListener(onStartup);

// listen for alarms
chrome.alarms.onAlarm.addListener(onAlarm);

Creating a repeating alarm is done like this:

// create a daily alarm to update live photostreams
function _updateRepeatingAlarms() {
    // Add daily alarm to update 500px and flickr photos
    chrome.alarms.get('updatePhotos', function(alarm) {
        if (!alarm) {
            chrome.alarms.create('updatePhotos', {
                when: Date.now() + MSEC_IN_DAY,
                periodInMinutes: MIN_IN_DAY
            });
        }
    });
}